A new idea to harness the energy of black holes

Fifty years ago, English mathematical physicist and Nobel Laureate Roger Penrose proposed that energy could be extracted from space around a rotating black hole. Known as the ergosphere, this region lies just outside an event horizon, the limit within which nothing can escape the gravitational pull of a black hole (even at the light). It is also here that infallible matter is accelerated to incredible speeds and emits all kinds of energy.

This became known as the Penrose process, which many theorists have since developed. The latest comes from a study conducted by researchers at Columbia University and Universidad Adolfo Ibáñez in Chile. With the support of organizations like NASA, they demonstrated how a better understanding of the physics at work around rotating black holes could one day allow us to harness their energy.

The study, titled “Magnetic Reconnection as a Mechanism for Extracting Energy from Rotating Black Holes,” was conducted by Luca Comisso and Felipe A. Asenjo. In it, they propose a new method by which energy could be harnessed from a black hole by breaking and joining magnetic field lines near its event horizon, the limit within which nothing can escape the gravitational pull (even in light) of a black hole.

As Comisso, a research scientist at Columbia University and the study’s first author, explained in a Columbia News press release:

“Black holes are usually surrounded by a hot ‘soup’ of plasma particles that carry a magnetic field. Our theory shows that when the magnetic field lines disconnect and reconnect, in the right way, they can accelerate the plasma particles into negative energies and large amounts of black hole energy can be extracted.

While Penrose theorized in 1971 that this process of particle decay could draw energy from a black hole, Stephen Hawking proposed in 1974 that black holes could release energy by emission of quantum mechanics (known as Hawking radiation name). This was followed by Roger Blandford and Roman Znajek suggesting in 1977 that electromagnetic torque was the main agent for extracting energy.

For the sake of their study, Comisso and Senjo considered a key part of the Penrose process, namely how the magnetic field lines separate and reconnect near the event horizon. This causes the infallible matter to transform into two streams of charged particles (aka plasma), one of which will be pushed against the spin of the black hole and pick up negative mass energy, causing it to fall beyond the horizon. events in the black hole. .

Meanwhile, the other plasma stream will be propelled in the same direction as the black hole’s rotation, allowing it to pick up additional mass-energy and escape to the ergosphere. Inside the ergosphere, the reconnection of magnetic field lines is so extreme that plasma particles are accelerated to speeds approaching the speed of light (aka. Relativistic speeds).

What this essentially means is that a black hole will lose energy by eating energy particles of negative mass. Additionally, the high relative velocity between captured and escaping plasma streams is what enables the process where huge amounts of energy can be extracted from a black hole. As Asenjo, professor of physics at the Universidad Adolfo Ibáñez and co-author of the study, explained:

“We calculated that the process of energizing the plasma can achieve an efficiency of 150%, far superior to that of any power plant operating on Earth. Achieving greater than 100% efficiency is possible because black holes leak energy, which is distributed free to plasma escaping from the black hole. “

While this may sound like science fiction, it is entirely possible that future generations will look to black holes for their energy needs. Additionally, Comisso and Asenjo argue, the energy extraction process may already be taking place with a number of black holes in the observable Universe. This may be the reason for black hole eruptions, which are powerful bursts of radiation that can be detected from Earth.

“In thousands or millions of years, humanity may be able to survive around a black hole without harnessing the energy of stars,” Comisso said. “It’s basically a technological problem. If we look at physics, nothing prevents it. “

In fact, it is possible that sufficiently advanced species in our Universe are already exploiting black holes for their unlimited energy. Such a scenario was recently suggested in an article by Marion Cromb, Ph.D. student of astrophysics at the School of Physics and Astronomy at the University of Glasgow. It is also a component of the transcension hypothesis, a proposition for the resolution of the Fermi paradox initially proposed by Roger Smart in 2002.

As well as being an ultimate energy source, Smart also suggested that black holes would allow a “transcendent” (super-advanced) species to create “an optimal domain in terms of computation of increasingly dense scales. , productive, miniaturized and efficient in space, time, energy and matter. There’s even the chance to study alternative physics models, time travel, and see the “seeds” of new universes!

There are also theories about how tiny black holes could be used to power an interstellar spacecraft (the black hole drive), or how an event horizon could become a means of propulsion (the Halo Drive). ). The latter idea works in much the same way as a gravity-assisted maneuver, where a spacecraft would use the event horizon of a rotating black hole to hurl toward distant stars at speeds approaching midnight. speed of light.

But in the meantime, studies like this are part of a growing effort to expand our knowledge of black holes and the exotic physics that take place in their vicinity. As Asenjo pointed out, theoretical studies of the physics of black holes are particularly important at a time when global efforts like the Event Horizon Telescope (EHT) are capturing the first images of black holes:

“Our increased knowledge of how magnetic reconnection occurs near the black hole could be crucial in guiding our interpretation of current and future telescope observations of black holes, such as those from the Event Horizon Telescope.

The study, recently published in the scientific journal Physical examination D, was made possible by funding provided by NASA, the Chilean National Fund for Scientific and Technological Development (FONDECYT) and the National Science Foundation (NSF) Windows on the universe initiative – a synthesis program that aims to bring together theoretical physics and observational astronomy under one roof to answer some of the deepest questions.

Further reading: Columbia News, Physical examination D